Tanning with complex basic zirconium sulphates



Patented Dec. 2, 1941 OFFICE TANNING wrrn ooMrLEx' BASIC zmoo- NIUM SULPHATES' Ian 0. Somerville, Philadelphia, Pa., Harold. G. Turley, Moorestown, N. .L, and Loren 0. Hui-d, Glenside, Pa.,assignors to Riihm & Haas Company, Philadelphia, Pa.

No Drawing. Application July 18, 193 Serial No. 285,082

of mineral tannage. It concerns particularly an improved and advantageous method of tanning I leather with complex, basic zirconium sulphates.

In U. S. Patent No. 1,940,610 itwas shownthat zirconium salts give a stable tannage. The preferred process consisted in tanning with zirconium sulphate in strongly acid solution. It has since been found that in some' instances tannage is effected in this way too rapidly and zirconium sulphate is too astringent. In all cases, moreover, the leather tanned with zirconium sulphate requires a large amount of alkali for subsequent neutralization. While a. range of basicities was envisaged by the patent, subsequent experience has demonstrated that some aqueous solutions of pure 50% basic zirconium sulphate are unstable on standing, even at room temperature, and hence its use in tanning leather suffers from the disadvantages based on its instability and lack of solubility.

It is the object of this invention to improve the process'of tanning with zirconium sulphate so that the advantages of basic sulphate may be utilized in a, practical way. It is another object of this invention to provide a process whereby pickled skins may be tanned directly with basic zirconium sulphates without troublesome adjustment of solutions during tanning and addition of other materials. It is also an object to produce zirconium-tanned leather which is more mellow and which may be more easily neutralized than has been previously possible. Another object is to provide a process for'the preparation of suede leather or buckskin leather of a markedly superior grade.

These objects are accomplished by preparing basic, double sulphates of zirconium, and ammonia, amines, or alkali metals, and treating; hides and skins therewith. Pickled stock may also be thus treated. The use of double zirconyl sulphates gives a milder action on hide or skin and produces more mellow leather than has pre-- viously been attained with zirconium salts.

to those exactly 50% basic.

for tanning and the solution is used in this form, if desired. These solutions are stable on standing at atmospheric temperatures, some of them having been kept for as long as nine months during which time no precipitation occurred. They may usually be heated to 50 or, C. without causing precipitation, depending on the particular composition.

The success of obtaining clear solutions depends in part upon the neutralizing agent or agents and the way in which they are used. The use of alkali hydroxides, such as potassium or sodium'hydroxldes or ammonium hydroxide, .is possible if they are added slowly and with good stirring; otherwise precipitation occurs. With care basicities may be reached ranging as high as 60%. Also, it is possible to add sodium hydroxide at the .start, if so desired, and then to carry thebasicity to fully sixty per cent. by the careful addition of an alkali carbonate, such as soda ash, or by the addition of ammonium hydroxide. By the use of solutions .ofsoda ash, basicities between 60% and have been reached without precipitation. By the use of other salts of a strong base and a weak acid, such as sodiumacetate, the apparent basicity may be carried even further. Thus, satisfactory solutions of basic zirconium sulphate containing sodium acetate suflicient to neutralize of the strong acid present have been made. 'Aliphatic amines can also be used to increase the basicity of solutions of zirconium sulphate.

As a further development of this discovery, it has been found that solutions of about 50% basic zirconium sulphate prepared in the above manner can be concentrated toyield a mixed or complex salt of zirconyl sulphate and the sulphate of the alkali used in neutralization. In cases where an excess of alkali sulphate is present, thesolution may be taken to dryness and a mixture of salts obtained. Starting with a solution of pure zirconium sulphate'and adding the theoretical amount of alkali, such as ammonia or caustic potash, under correct conditions crystallization of a double salt of definite chemical composition takes. place which may be purified and dried.

These dry salts are quite readily soluble in water and can be used in tanning in the same way as solutions containing basic zirconium sulphate. The convenience is obvious of securing these materials in'dry form in this simple way and so facilitating packing and shipp n The preparation of dry materials is not limited P ducts have been prepared showing 35% basic- Some water-soluble ity, some as high as 66% basicity, so that a wide range of b'asicity is obviously permissible.-

t In addition to dry salts of the above types, it has also been found possible to utilize mixed complex basic sulfates of zirconium and chrmium, zirconium and aluminum, or zirconium, aluminum, and chromium. They have been prepared in dry form and can be very simply utilized in the same way as above.

The general method of tanning with basic double sulphates is to prepare a solution of them in water and to add this solution to hides or skins in brine solution. Alternatively in many cases it is possible simply to add the tanning salt in a dry form and allow it to dissolve as the skins are drummed in the brine solution. This is of special advantage when it is desired to tan in a very concentrated solution, as no water need be added along with the tanning material. When penetration is complete, the skins are either neutralized in the same liquor or are drained and neutralized in fresh water or are rinsed until free from strong acid.

While pickled stock of acid reaction is most commonly tanned by this procedure, it is also possible to tan skins which have been depickled to show a pH around 5, and even to treat skins initially on the alkaline side of the iso-electric point with zirconium sulphate of at least 40% basicity so as to produce a leather of surprisingly good mellowness.

A wide variety of neutralizing agents may be employed with the basic sulphate but, in general, it is preferable and most convenient to use a weak alkali or an alkaline salt of a weak acid, such as soda ash, bicarbonate of soda or potash, borax, sodium silicate, ammonium bicarbonate, a sodium phosphate, sodium acetate, sodium phthalate, etc. Another method of neutralization is to treat with a salt of a. non-tanning sulphonic acid, or a condensed sulphonic acid, or

to use a neutralized synthetic tanning material. Examples of such salts include the alkali and alkaline earth salts of sulphonic acids of aromatic hydrocarbons or phenols such as naphthalene, diphenyl, naphthol, phenol sulphone, or salts of condensation products of such sulphonic acids with aldehydes or ketones, or salts of condensation products of the unsulphonated compounds solubilized by treatment with an aromatic sultanning agents, and reactive aldehydes such as formaldehyde. Zirconium tonnage mayprecede or follow tanning with these other tanning. agents or, as shown, may often be jointly effected therewith.

The following examples illustrate the method of using these materials in the tanning of hides or skins.

Example 1 100 lbs. of shaved pickled kidskins were drummed in 200 lbs. of water containing 12 lbs. of sodium chloride and a solution of basic zirconium sulphate, containing the equivalent of 7 lbs. of zirconium oxide, was added in one feed. This solution was prepared from an aqueous solution of zirconium sulphate by adding sufficient ammonium hydroxide slowly with stirring to neutralize 50% of the acid present. After drumming for six hours'the skins were removed and left on the horse overnight. Next day they were neutralized with borax in fresh water, washed. iatliquored and crusted. The subsequent processing followed the usual methods for making suede leather-and after the final bufling the skins showed a remarkably fine nap. They had a white color and good strength.

Example 2 A solution of zirconium sulphate was made 40% basic by the addition of the calculated amount of soda ash and diluted to contain the equivalent of 10% zirconium oxide. After'standing at room temperature for six months, this was used to tan pickled calfskin as follows:

100 lbs. of pickled calfskins were drummed in 200 lbs. of water containing 15 lbs. of sodium sulphate, and 50 lbs. of the above solution was added phonic acid and an aldehyde such as formaldehyde.

The skins are finally thoroughly washed, fatliquored, and treated with pigment if desired.

This tannage can be used for the preparation of grain finished leather. with proper care and selection of skins, a smooth grain can be secured. On the other hand, it is possible to secure a "raised" or so-called crushed" grain effect. Particularly fine results can be secured in thepreparation of suede leather when a very smooth, fine nap can be obtained in conjunction with excellentstrength. In general these advantages hold for all types of buffed or snufied leather.

In general, this tannage is most desirable for the preparation of white leather, but the leather can be colored in the usual way for mineraltanned leather, and offers the possibility of producing very bright, pure shades in a simple, direct manner.

In'addition to the use of these materials .in

tanning by themselves, they can be used as auxiliary tanning agents in conjunction with other materials such as salts of alum, iron, or chromium, the various organic ynthetic and natural 7 5 in three feeds at half-hour intervals. Drumming was continued for five hours, and the skins left in the liquor overnight with occasional drumming. Next day the skins were neutralized in the same liquor with sodium bicarbonate to a pH of 4.5, shaved, washed, and fatllquored with a sulphonated oil, followed by the addition of a white pigment. After horsing overnight the skins'were set outon the grain and crusted, then finished as usual for smooth, white, calf upper leather.

Examples A dry salt was prepared by the addition of potassium carbonate to a solution of zirconium sulphate, the solid which separated being purified and dried.- It showed a composition corresponding to K2804. 8ZrOSO4. 22340. This had low olubility in water but was used satisfactorily in tanning as described below.

lbs. of pickled kidskins were drummed in 300 lbs. of water containing 15 lbs. of sodium chloride, and 12 lbs. of this tanning salt was added in five portions at half-hour intervals.

Drumming was continued until penetration was drummed in 50 lbs. of water containing lbs. of sodium chloride, and 12 lbs. of this tanning salt added in one feed. Drumming was continued four hours, the skins horsed overnight, then neutralized with sodium' silicate and finished as in Example 1.

Example 5 A complex salt was prepared in dry form by the addition of sufficient dimethylamine to a solution of zirconium sulphate to give a, basicity of tralized by the addition of. sodium thiosulphate,

washed, fatliquored with a sulphonated oil along with a small amount of an emulsifying agent. and dried. After staking, a soft, white leather with smooth grain was obtained.

.The same procedure was followed with a double salt prepared from zirconium sulphate and triethanolamine. A high grade of white leather was likewise produced.

' Example 6 A dry salt of highbasicity was prepared by the addition of soda ash to a solution of zirconium sulphate in amount sufiicient to give a basic-, ity of 65%. The turbid solution first obtained cleared up on longer stirring, and was then evaporated to dryness. It was usedto tan pickled calfskins as follows:

100 lbs. of calfskins which had been given a high pickle. were drummed in 200 lbs. of water containing 15 lbs. of sodium sulphate, and. 16 lbs. of the taming salt was added in four portions at half-hour intervals. Drumming was continued until penetration was complete. Then the skins were neutralized with ammonium bicarbonate to a pH of 3.5 and rinsed. The skins were then retanned in a convenient amount of water at 80 F. by the addition of 5 lbs. of a syntan made according to U. S. Patent No. 2,129,553.

After washing and fatliquoring. they were finished as in Example 2.

Example 7 100 lbs. of kangaroo skins, which had been unhaired and adjusted to show a pH of 6 on spotting with an indicator, were drummed in 150 lbs. of water containing 10 -lbs. of sodium chloride, and 50 lbs. of the solution of 40% basic zir-,

conium sulphate described in Example 2 was added in one feed. When penetrationwas complete, the liquor-was drained and the skins then neutralized, washed, fatliquored and crusted. After staking, they were buffed and finished in the normal manner for suede leather.v

Example 8 Example 9 A complex, dry salt was prepared by the ad-' dition of 33% basic chromium sulphate containing a small amount of aluminum sulphate to a' solution of zirconium sulphate, and evaporation to dryness. It showed the following composition by analysis: 12.6% CraOa, 2.0% A1203, 19.4% ZrOz, 21.4% water, and was used in tanning as follows:

lbs. of pickled kidskins' were drummedin 200 lbs. of water containing 10 lbs. of sodium chloride and 16 lbs. of this tanning salt added in one feed, drummed until penetration was complete, neutralized in the same liquor using sodium acetate, washed, fatliquored. and crusted. After staking, these skins had a pale bluishwhite color, lighter than was obtained by the use of chrome tannage alone.

' EztampleIO 100 lbs. of pickled skivers were tanned in 200 )lbs. of water containing 15 lbs. of sodium chlorideby theaddition of 17 lbs-of the dry ainmonium zirconium sulphate used in Example 4. When penetration was complete, 3 lbs. of a neutral salt made by condensation of naphthalene sulphonic acid 'with formaldehyde was added and the drum run for one hour. The skins were then washed, fatliquored, and crusted. After staking, a soft, mellow, white leather was secured. A similar type of leather with a light uniform pastel tint was secured by repeating .this processand coloring with 0.25% of an acid dye before fatliquoring.

Example 12 100 lbs. of pickled sides from steerhides were drummed in 200 lbs. of water containing 10 lbs. of sodium chloride and 10 lbs. of the dry ammonium zirconium sulphate used in Example 4 was added. After five hours borax was added while the drum was running until the skins showed a uniform pH of 3.5. After draining, the skins were taken up in a convenient amount of water and 30 lbs. of a.commercial'quebrachoextract added in two feeds half an hour apart. Drumming was continued until the vegetable tannin was well taken up, then the skins were washed, fatliquored and dried in the usual way.

chloride and 25 lbs. of this tanning salt was added in one feed. After drumming for four hours the skins were horsed overnight, neutralized in 'fresh water with sodium acetate, and processed as in, Example 5.

Tanning with basic double sulphates of zirconlum and analkali metal, ammonia, or amine. gives results which are superior in softness and mellowness to those which are obtained with other zirconium salts. Our work has shown conclusively that the basic. sulphates give tannage which is better than that obtained with the chlorides. When it is desired to secure the maximum effect from zirconium sulphates. tannage can be performed in a solution of sodium sulphate instead of the usual sodium chloride brine solution. The addition of basic sulphates permits the exclusion of chloride ions completely.

' By the use of basic double salts tanning can be accomplished without the further addition of materials to control the pH, the type of salt, or the course of the tannage. Simplicity and control of the process result with a saving in labor and time and greater certainty that a white, water-resistant, mellow leather will result.

When this improved process is applied to the making of suede leather, an outstanding result is secured. This is not confined to any one class of skin, as good results have been secured with kidskins, calfskins and kangaroo skins. 'It is also possible to prepare buckskin leather from deerskins and to make imitation buck by starting from side leather using cow or steerhide as the starting point and batting on the grain side, or to make the corresponding type of leather starting from the flesh split from cow or steer hides. We have found that this tannage simplifies the process of shaving, since the skins cut more easily than, for instance, chrome-tanned skins Also, in the buifing process for finishing suede or buckskin the leather made in this way is processed very easily, and so can be treated to yield a particularly fine nap, yet at the same time the valuable properties of mellowness and strength are preserved.

We claim:

1. In the process of tanning with zirconium salts, the improvement which comprises treating pickled skins with a solution containing a watersoluble, complex salt of basic zirconium sulphate and a sulphate of a salt-forming group selected from the class consisting of alkali metals, ammonia, and lower aliphatic amines.

2. In the process of tanning with zirconium salts, the improvement which comprises treating pickled skins in a solution of sodium sulphate with a water-soluble, complex salt of basic zirconium sulphate and a sulphate of a salt-forming group selected from the class consistingof alkali metals, ammonia, and lower aliphatic amines.

3. In the process of tanning with zirconium salts, the improvement which comprises drumming pickled skins in a small amount of sodium chloride brine with addition of a soluble, dry complex salt of basic zirconium sulphate and a sulphate of a salt-forming group selectedfrom the class consistingof alkali metals, ammonia, and lower aliphatic amines.

4. In the process of tanning with zirconium Eli salts, the improvement which comprises drumming pickled skins in a small amount of sodium chloride brine with addition of a soluble, dry

complex salt of zirconium sulphate of basicity 35-65% and a sulphate of a salt-forming group selected from the class consisting of alkali metals, ammonia, and lower aliphatic amines.

5. In the process of making leather, the improvement which consists in the application 01' a water-soluble composition comprising a complex salt of basic zirconium sulphate and a sulphate of a member of the salt-forming group consisting of alkali. metals, ammonia, and lower. aliphatic amines.

6. In the process of tanning with zirconium salts, the improvement which comprises treating pickled hides with a solution containing a complex salt of ammonium sulphate and zirconyl sulphate.

"7. In the process of tanning with zirconium salts, the improvement which comprises treating pickled hides with a solution containinga complex salt of sodium sulphate and zirconyl sulphate.

8. A mineral tanning material which consists substantially of a dry, water-soluble, basic double sulphate of zirconium and a member of the saltforming group consisting of alkali metals, ammonia, and lower aliphatic amines.

9. A mineral tanning material which comprises a complex salt of a water-soluble, basic zirconium sulphate and a sulphate of a member of the saltforming group consisting of alkali metals, ammonia, and lower aliphatic amines.

10. A process of tanning which comprises treating hides with a solution containing a complex salt of ammonium sulphate and zirconyl sulphate and subsequently neutralizing with the salt of a strong base and a weak acid.

11. The process of tanning which comprises drumming pickled skins in a solution containing a water-soluble composition comprising a complex salt of a basic zirconium sulphate and a sulphate of a member of the group consisting of alkali metals, ammonia, and lower aliphatic amines, and subsequently neutralizing with a salt of an aromatic sulphonic acid.

IAN C. SOLIERVILLE. HAROLD G. 'I'URLEY. LOREN C. HURD. 

